Process for the manufacture of hydraulic cement



Patented May 14, 1929 UNITED STATES 1,713,172 PATENT OFFICE.

ROBERT nn LUCE, or nos ANGELES, CALIFORNIA.

PROCESS FOR THE MANUFACTURE OF HYDRAULIC CEMENT.

No Drawing.

As is well known, or generally believed, the principal constituent of Portland cement isa chemical combination of lime, sil

. alumina, in proper proportions accompanied.

being applicable generally to all such cement by other materials such as compounds of iron and magnesia. Many mineral deposits are encountered, the chemical compositions of which indicate that they should be suitable for use in the manufacture of Portland cement, but which are not suitablefor commercial use due to the high temperature required for clinkering.

An object of the present invention is to devise a commercially feasible process of making hydraulic cement capable of making use ofsuch refractory cement-making materials.

The process of the present invention is applicable to the refractory cement-making materials referred to,but is not limited thereto,

making materials containing lime, alumina, and silica with or Without impurities as are theoretically suitable for use in the produc tion of Portland cement.

In accordance with my invention an excessively high clinkering temperature for bringing about the necessary. combination of the lime, alumina, and silica is avoided by first subjecting the raw cement-making materials to a preliminary treatment whereby the lime, silica, andalumina are chemically combined or brought into a condition in which they readily combine at temperatures not substantially exceeding those ordinarily employed in clinkering Portland cement mixtures.

The first step of the process of my pre ent invention is similar to the process dis-. closed in my Patent No. 1,345,077, dated June 29, 1920. The process of said patent is designed for the production of fertilizer material and consists generallyin subjecting an aqueous mixture of burned limestone or lime and feldspar or similar potash bearing mineral to vigorous agitation with live or superheated steam at a high temperature,

.parently combine forming Application filed January 11, 1927. Serial No. 160,524.

above 100 and preferably from 200 to 250, C. and under high pressure, say 200 pounds steam pressure. This treatment preferably is carried out by conducting the aqueous mixture into a closed steel autoclave having a cone bottom into which live steam is admitted. The treatment ordinarily re quires from two to six hours. As a result the potash bearing rock is decomposed and the alkali metals rendered soluble as hydroxides, while the lime, silica, and alumlna apci'um aluminium silicate.

In accordance with the present invention, the principal object of which is the production of hydraulic cement rather than fertilizer material the raw materials are mixed in proper proportions to give a limealumina-silica ratio within the range required for the production. of Portland cement. This ratio is well known, but for convenience may be stated here as being in the neighborhood of CaO 62.0 parts by weight an insoluble cal- ALO -r 7.5 parts by weight Sit); 22.0 parts by weight g or 2.8 parts of lime to each part of silica and 1.1 parts of'lime to eachpart of alumina.

As stated, the first step of the process to, may be applied to mixtures of lime and feldspar or to other suitable mixtures providing the desired ratio of lime, alumina and silica, such as mixtures of burned lime, sand. and clay. Regardless of the starting material employed the product 'of the preliminary treatment is separated by filtration. sedimentation or in any other suitable way, and the liquid, in case feldspar or other ma terial containing soluble valuable components has been used, may be treated for their recovery, such treatment being no part, of my present invention. The insoluble por-' tion, which, if the starting materials have been properly proportioned, will consist essentially of lime, silica, and alumina in chemical combinationf in the proportions necessary for the formation of Portland cement and will be free or substantially free of deleterious materials such as the alkalies. This material is dried and calcined at a temperature of approximately 2800 to 2500 tant advantage of my invention resides in the calcining operation. The temperature required, 2300 l*., is below the average clinkering temperature for Portland cement and consequently the ordinary clinkering apparatus may be used even though the original starting materials may have been such that they could not be made into cement Without the use of excessively high temperatures with incident disadvantages, such as high fuel consumption and rapid destruction of the clinkering apparatus. In accordance with my invention the mintmfe or chemical combination of lime, alumina, and silica need be heated only up to the point at which incipient fusion first becomes apparent and it is not necessary to completely vitrify in the ordinary l ortland cement making process Consequently the temperature required is lower and the time required is shorter than in standard cement male ig )ractiee. Due to the fact that the mate i is not clinkered or vitrified in the usual cement making process, but only slightly fused, the product of the heating operation is quite soft and easily ground as 'nnpared with ordinary cement clinker. Also due to the fact that fusion not required. the use or raw material containing iron compounds serving as a flux may be dispensed with and the resulting cement may therefore be vvl As is apparent when feldspar or similar pot-ash containing material is used to supply the silica and alumina ingredients oi the cement, the potash is recovered aval uable by-produet.

I claim:

1. Process for the production of hydraulic cement which comprises digesting an aqueous mixture comprising lime, silica, and alumiin proportions suitable for the production of Portland cement at a temperature of at least 100 n under superatmospheric pressure and with violent agitation until the lime, si ica, and alumina are combined as an insoluble calcium aluminium silicate,and heat 3 said insoluble calcium aluminium silica to the point at which fusion first becomes apparent.

2. Process for theproduction of hydraulic cement whichcomprises heating the insoluble residue of: the dige tion. under vigorous agjtation with live steam at superatmospheric pressure of a mixture comprising lime, alumina, and silica in substantially the PIGPOL'l lODS of 2.8 parts by weight of lime to 1 part by Weight of silica and 1.1 parts by Weight of lime to 1 part by Weight of alumina to a temperature of about 2800 F.

to 2500 F. until fusion first becomes apparent.

3. Free for the production of hydraulic cement which comprises subjecting a mixture of lime with minerals containing alumina and silica in proportions to produce Portland cement to vigorous agitation with live an at a temperature of 200 to 250 and under a pressure oi? at least 200 pounds per iquarc inch, separating and dryin the insoluble residue, heating the dried l8.--lltll1 to a temperature of about 2800 l until fusion first becomes apparent, and pul verizing the resulting material.

In testimony whereof, I al'lix my signature.

ROBERT DE LUCE. 

